President Donald Trump urged women Monday not to take a common over-the-counter fever-reducer and pain-reliever during pregnancy, linking Tylenol as well as the childhood vaccine schedule to an increased risk of autism.

Trump’s remarks on vaccines — which appeared to be off-the-cuff — marked his clearest endorsement yet of a connection between the shots received early in childhood and the rise in autism diagnoses — a theory long rejected by scientists.

In the hours before his remarks, Trump supporters who want the president and his health officials to explicitly link autism to childhood vaccines — despite decades of data refuting a connection — fretted that the administration might shy away from doing so despite longtime anti-vaccine advocate Robert F. Kennedy Jr.’s leadership of the health department. Trump made it clear he endorsed Kennedy’s continued review of vaccine safety.

On Tylenol, Trump vacillated between echoing what his health officials advised — saying the federal government is “strongly recommending that women” limit use in pregnancy “unless medically necessary” — and staking out his own position more forcefully.

“I’m not so careful with what I say,” he said, before adding: “Taking Tylenol is not good. Alright, I’ll say it: It’s not good.”

The FDA will notify doctors that Tylenol as well as generic acetaminophen “can be associated with a very increased risk of autism,” Trump said.

That message contradicts a recent analysis of nearly four dozen studies investigating a potential connection between acetaminophen use during pregnancy and neurodevelopmental conditions. That study, co-authored by the dean of the faculty at Harvard T.H. Chan School of Public Health, found reason to be concerned about a connection and said women should be warned, but also advised against broad limitations in favor of a “balanced approach” that acknowledges the risks of untreated fever and pain during pregnancy.

Other studies, including a study that harnessed data on nearly 2.5 million children born in Sweden between 1995 and 2019, have found no correlation between acetaminophen and autism.

American College of Obstetricians and Gynecologists President Steven Fleischman called the acetaminophen announcement “not backed by the full body of scientific evidence and dangerously simplifies the many and complex causes of neurologic challenges in children.”

“Suggestions that acetaminophen use in pregnancy causes autism are not only highly concerning to clinicians but also irresponsible when considering the harmful and confusing message they send to pregnant patients, including those who may need to rely on this beneficial medicine during pregnancy,” Fleischman said in a statement.

Trump also touted the potential for a medication commonly used to counteract chemotherapy side effects to treat certain children with autism. While scientists say leucovorin, a form of vitamin B, could be promising for a subset of patients, they cautioned that the current data is limited and the drug needs more research.

Three senior health officials — NIH Director Jay Bhattacharya, FDA Commissioner Marty Makary and CMS Administrator Mehmet Oz — wrote in a POLITICO Magazine opinion piece published Monday that they would fast-track approval of leucovorin as a treatment for kids with symptoms of autism and cerebral folate deficiency. That move will unlock insurance coverage by government programs for low-income people, Medicaid and CHIP, which cover more than half of American children.

The lead-up to Trump’s remarks spurred doctors to warn that they could prompt pregnant women to avoid acetaminophen in situations where its use is warranted — and to blame themselves if their children receive an autism diagnosis.

Acetaminophen is one of the few over-the-counter drugs recommended during pregnancy to treat fever and pain, as alternatives like ibuprofen are known to increase the risk of birth defects. High fever during pregnancy also poses risks to a developing fetus for complications, such as neural tube defects.

“There’s this catch-22 where a mother is always to blame,” Danielle Hall, director of healthy equity at the Autism Society of America, said, referring to a since-discredited mid-20th century theory pinning autism’s cause on emotionally cold mothers.

Ann Bauer, a University of Massachusetts at Lowell researcher who worked on the study with the Harvard dean that drew the Tylenol-autism connection, told POLITICO the science requires “a nuanced message” that acknowledges the potential risks of both the drug and untreated pain or fever.

“It’s not black and white, and I think that’s part of the issue with the medical community communicating this,” she said. “Acetaminophen may still be your best option. But the risks from acetaminophen are much greater for prolonged use than it is for taking it a few times, and I think that we have to be very concerned that a woman would — because of these warnings — might not take it when she should.”

Before Trump’s announcement – which he previewed Sunday at the memorial service for the assassinated conservative leader Charlie Kirk – some of his allies who are suspicious of vaccines complained he was taking the focus off vaccines as a cause of autism.

On Monday, Trump reassured them. “They pump so much stuff into those beautiful little babies, it’s a disgrace,” he said of vaccines.

Mary Holland, CEO of the Kennedy-cofounded anti-vaccine group Children’s Health Defense, said the group still believes vaccines are driving the increase in autism diagnoses in the U.S. — and that Kennedy hasn’t finished his work.

“I can’t imagine that this is the end of the story,” she told POLITICO. “I think this is the beginning of a process.”

David Lim and Mari Eccles, a reporter at POLITICO-EUROPE, contributed to this report.